Concept:The yield point marks the end of elastic behaviour and the start of plastic deformation.Explanation:When a loaded wire is stretched, its molecules initially return to their original positions if the load is removed.Beyond the elastic limit, the wire reaches the yield point.At the yield point, the molecules begin to slide across each other permanently.This sliding causes a rapid increase in extension even with a small increase in load.Therefore, the correct description matches the yield point.Answer:A. yield point